Leveling Fade Height default setting (#20316)

Marlin/Configuration.h

   // at which point movement will be level to the machine's XY plane.
   // The height can be set with M420 Z<height>
   #define ENABLE_LEVELING_FADE_HEIGHT
+  #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
+    #define DEFAULT_LEVELING_FADE_HEIGHT 10.0 // (mm) Default fade height.
+  #endif
 
   // For Cartesian machines, instead of dividing moves on mesh boundaries,
   // split up moves into short segments like a Delta. This follows the

Marlin/src/inc/Conditionals_post.h

   #endif
 #endif
 
+#ifndef DEFAULT_LEVELING_FADE_HEIGHT
+  #define DEFAULT_LEVELING_FADE_HEIGHT 0.0
+#endif
+
 #if ENABLED(SEGMENT_LEVELED_MOVES) && !defined(LEVELED_SEGMENT_LENGTH)
   #define LEVELED_SEGMENT_LENGTH 5
 #endif

Marlin/src/module/settings.cpp

     // Global Leveling
     //
     {
-      const float zfh = TERN(ENABLE_LEVELING_FADE_HEIGHT, planner.z_fade_height, 10.0f);
+      const float zfh = TERN(ENABLE_LEVELING_FADE_HEIGHT, planner.z_fade_height, (DEFAULT_LEVELING_FADE_HEIGHT));
       EEPROM_WRITE(zfh);
     }
 
   //
   // Global Leveling
   //
-  TERN_(ENABLE_LEVELING_FADE_HEIGHT, new_z_fade_height = 0.0);
+  TERN_(ENABLE_LEVELING_FADE_HEIGHT, new_z_fade_height = (DEFAULT_LEVELING_FADE_HEIGHT));
   TERN_(HAS_LEVELING, reset_bed_level());
 
   #if HAS_BED_PROBE